U.S. patent number 5,436,560 [Application Number 08/122,591] was granted by the patent office on 1995-07-25 for method and device for detecting electromagnetic characteristic changing portion.
This patent grant is currently assigned to Kabushiki Kaisha Komatsu Seisakusho. Invention is credited to Taku Murakami.
United States Patent |
5,436,560 |
Murakami |
July 25, 1995 |
Method and device for detecting electromagnetic characteristic
changing portion
Abstract
A method for sensing with a high accuracy a single part, at
which electromagnetic characteristics of a member to be sensed are
changed, and for obtaining the output whose waveform is of a narrow
peak width, and the device thereof. For this purpose, four
electromagnetic sensing elements (10A-10D) are so aligned that when
the two elements (10A, 10B) are simultaneously in the positions
just over a protruding part (16) where electromagnetic
characteristics are changed, the other two elements (10C, 10D) are
in the positions just over a recessed part (18). Further, the
mutually opposing two arms of a bridge circuit (30) are connected
with one of the electromagnetic sensing elements (10A, 10B) and one
of the elements (10C, 10D) respectively. Thereby, a single output
having a waveform corresponding to the part at which the
electromagnetic characteristics are changed is sensed.
Inventors: |
Murakami; Taku (Hiratsuka,
JP) |
Assignee: |
Kabushiki Kaisha Komatsu
Seisakusho (Tokyo, JP)
|
Family
ID: |
14024035 |
Appl.
No.: |
08/122,591 |
Filed: |
September 29, 1993 |
PCT
Filed: |
March 24, 1992 |
PCT No.: |
PCT/JP92/00352 |
371
Date: |
September 29, 1993 |
102(e)
Date: |
September 29, 1993 |
PCT
Pub. No.: |
WO92/17749 |
PCT
Pub. Date: |
October 15, 1992 |
Foreign Application Priority Data
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Mar 29, 1991 [JP] |
|
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3-091353 |
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Current U.S.
Class: |
324/207.21;
324/207.25 |
Current CPC
Class: |
G01B
7/003 (20130101); G01D 5/142 (20130101); G01D
5/147 (20130101); G01D 5/2451 (20130101); G01P
3/488 (20130101) |
Current International
Class: |
G01B
7/00 (20060101); G01D 5/12 (20060101); G01P
3/42 (20060101); G01D 5/16 (20060101); G01D
5/245 (20060101); G01P 3/488 (20060101); G01B
007/14 (); G01R 033/06 () |
Field of
Search: |
;324/207.12,207.2,207.21,207.25,173,174,235,251,252 ;338/32R |
Foreign Patent Documents
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56-1567 |
|
Jan 1981 |
|
JP |
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59-146720 |
|
Oct 1984 |
|
JP |
|
Primary Examiner: Snow; Walter E.
Attorney, Agent or Firm: Richards, Medlock & Andrews
Claims
I claim:
1. A method for detecting an electromagnetic characteristic
changing portion comprising the steps of:
aligning four electromagnetic sensing elements and a member, having
the electromagnetic characteristic changing portion to be detected,
in a row in a direction of a relative movement therebetween;
positioning the four electromagnetic sensing elements within the
row in such a manner that, when two out of the four sensing
elements are simultaneously located at a position corresponding to
said electromagnetic characteristic changing portion as a result of
relative movement, the remaining two sensing elements are located
at a position not corresponding to the electromagnetic
characteristic changing portion; and each of these four
electromagnetic sensing elements is connected in a respective one
of the four sides of a bridge circuit, with each pair of opposing
sides of said bridge circuit containing one electromagnetic sensing
element located at a position corresponding to said electromagnetic
characteristic changing portion and one electromagnetic sensing
element located at a position not corresponding to said
electromagnetic characteristic changing portion, thereby detecting
the electromagnetic characteristic changing portion.
2. A device for detecting an electromagnetic characteristic
changing portion comprising:
a member having the electromagnetic characteristic changing portion
to be detected;
four electromagnetic sensing elements that move relatively to said
member having the electromagnetic characteristic changing portion
to be detected and that are aligned in a row in a direction of the
relative movement; said four electromagnetic sensing elements being
positioned within said row in such a manner that, when two out of
the four sensing elements are simultaneously located at a position
corresponding to said electromagnetic characteristic changing
portion as a result of relative movement, the remaining two sensing
elements are located at a position not corresponding to the
electromagnetic characteristic changing portion; and
a bridge circuit of which each of the four sides is formed of a
respective one of the four electromagnetic sensing elements;
wherein the outer two of said four electromagnetic sensing elements
aligned in a row are in two opposing sides, respectively, of said
bridge circuit and the inner two of said four electromagnetic
sensing elements are in the remaining two opposing sides,
respectively, of the bridge circuit.
3. A method for detecting an electromagnetic characteristic
changing portion, said method comprising the steps of:
aligning four electromagnetic sensing elements and a member, having
an electromagnetic characteristic changing portion to be detected,
in a row in a direction of relative movement therebetween;
positioning the four sensing elements within the row in such a
manner that, when two out of the four sensing elements are
simultaneously located at a position corresponding to said
electromagnetic characteristic changing portion as a result of
relative movement, the remaining two sensing elements are located
at a position not corresponding to the electromagnetic
characteristic changing portion, with each of these four
electromagnetic sensing elements being connected in a respective
one of the four sides of a bridge circuit with each pair of
opposing sides of the bridge circuit containing one electromagnetic
sensing element located at the position corresponding to said
electromagnetic characteristic changing portion and one
electromagnetic sensing element located at the position not
corresponding to said electromagnetic characteristic changing
portion; and
applying a magnetic field to the electromagnetic characteristic
changing portion, whereby said bridge circuit detects fluctuation
of magnetic flux caused by the electromagnetic characteristic
changing portion.
4. A method in accordance with claim 3, wherein said member has a
plurality of electromagnetic characteristic changing portions
aligned in the form of a scale.
5. A method in accordance with claim 4 wherein each electromagnetic
characteristic changing portion has a width of .lambda./2, each of
said four sensing elements has a corresponding width equal to or
slightly smaller than .lambda./4, and the pitch between adjacent
ones of said four sensing elements is equal to or slightly larger
than .lambda./4.
6. A method in accordance with claim 5, wherein said scale is in
the form of a graduation of concave portions and convex portions,
with each electromagnetic characteristic changing portion being one
of said convex portions.
7. A method in accordance with claim 3, wherein each sensing
element is a magneto-resistive element.
8. A method in accordance with claim 7, wherein each sensing
element is a ferromagnetic magneto-resistive element.
9. A method in accordance with claim 7, wherein each sensing
element is a semiconductor magneto-resistive element.
10. A method in accordance with claim 3, wherein the four
electromagnetic sensing elements are aligned in said row so that
there is an outer pair of sensing elements in said row and an inner
pair of sensing elements in said row, and wherein one pair of
opposing sides of the bridge circuit contains the outer pair of
electromagnetic sensing elements and the other pair of opposing
sides of the bridge circuit contains the inner pair of
electromagnetic sensing elements.
11. A method in accordance with claim 3, further comprising
obtaining from said bridge circuit a single output waveform
corresponding to the electromagnetic characteristic changing
portion.
12. A method in accordance with claim 11, wherein said single
output waveform has a narrow peak width, thereby allowing accurate
detection of a single electromagnetic characteristic changing
portion.
13. A method in accordance with claim 3, wherein said
electromagnetic characteristic changing portion is varied
cyclically and continuously.
14. A method in accordance with claim 3, wherein said magnetic
field is applied at an angle to the electromagnetic characteristic
changing portion.
15. A method in accordance with claim 14, wherein said angle is
about 45.degree..
16. A device for detecting an electromagnetic characteristic
changing portion, said device comprising;
a member having the electromagnetic characteristic changing portion
to be detected;
four electromagnetic sensing elements that move relative to said
member in a direction of relative movement, said four sensing
elements being aligned in a row in said direction of relative
movement such that there is an outer pair of sensing elements in
said row and an inner pair of sensing elements in said row; said
four electromagnetic sensing elements being positioned within said
row in such a manner that, when two out of the four sensing
elements are simultaneously located at a position corresponding to
said electromagnetic characteristic changing portion as a result of
relative movement, the remaining two sensing elements are located
at a position not corresponding to the electromagnetic
characteristic changing portion;
a bridge circuit having four sides, with each of said four sides
containing a respective one of said four electromagnetic sensing
elements, said outer pair of sensing elements being in two opposing
sides, respectively, of said bridge circuit, and said inner pair of
sensing elements being in the remaining two opposing sides,
respectively, of said bridge circuit; and
a means for applying a magnetic field to the electromagnetic
characteristic changing portion, whereby said bridge circuit
detects fluctuation of magnetic flux caused by relative movement
between the electromagnetic characteristic changing portion and
said four electromagnetic sensing elements in said direction of
relative movement.
17. A device in accordance with claim 16, wherein said member has a
plurality of electromagnetic characteristic changing portions
aligned in the form of a scale.
18. A device in accordance with claim 17 wherein each
electromagnetic characteristic changing portion has a width of
.lambda./2, each of said four sensing elements has a corresponding
width equal to or slightly smaller than .lambda./4, and the pitch
between adjacent ones of said four sensing elements is equal to or
slightly larger than .lambda./4.
19. A device in accordance with claim 18, wherein said scale is in
the form of a graduation of concave portions and convex portions,
with each electromagnetic characteristic changing portion being one
of said convex portions.
20. A device in accordance with claim 16, wherein each sensing
element is a magneto-resistive element.
21. A device in accordance with claim 20, wherein each sensing
element is a ferromagnetic magneto-resistive element.
22. A device in accordance with claim 20, wherein each sensing
element is a semiconductor magneto-resistive element.
23. A device in accordance with claim 16, wherein said
electromagnetic characteristic changing portion varies cyclically
and continuously.
24. A device in accordance with claim 16, wherein said means for
applying said magnetic field applies said magnetic field at an
angle to the electromagnetic characteristic changing portion.
25. A device in accordance with claim 24, wherein said angle is
about 45.degree..
Description
FIELD OF THE INVENTION
This invention relates to a method and a device for detecting an
electromagnetic characteristic changing portion formed on a member
to be detected, such as a position detecting device of a hydraulic
cylinder, a linear scale, or a rotary encoder.
BACKGROUND ART
Conventionally, in a position sensor or the like, an
electromagnetic characteristic changing portion consisting of
concave and convex grooves is formed on a scale; a magnetic field
is applied to the electromagnetic characteristic changing portion;
and an electromagnetic sensing element, such as a ferromagnetic
thin-film magneto-resistive element, is used to detect fluctuation
of magnetic flux caused by the electromagnetic characteristic
changing portion. To detect the fluctuation of magnetic flux with a
high sensibility, a bridge circuit can be made up of four
magneto-resistive elements.
More particularly, as shown in FIG. 4(A), four magneto-resistive
elements 10a through 10d are arranged along a graduation 14
consisting of concave and convex grooves formed on a scale 12.
Then, when the magneto-resistive element 10a and the next
magneto-resistive element 10c but one are simultaneously located at
positions corresponding to a convex region 16 of the scale 12, the
remaining two magneto-resistive elements 10b and 10d are located at
positions corresponding to a concave region 18.
Furthermore, the magneto-resistive elements 10a through 10d
constitute, as shown in FIG. 4(B), a bridge circuit 20 that serves
as a detection circuit. More particularly, the cross-hatched
magneto-resistive elements 10a and 10c that arrive simultaneously
to the positions corresponding to the convex regions 16 compose two
opposing sides of the bridge circuit 20. The magneto-resistive
elements 10b and 10d that arrive to the positions corresponding to
the concave regions 18 compose the other two opposing sides of the
bridge circuit 20. In this event, if Ra through Rd denote
electrical resistance of the magneto-resistive elements 10a through
10d, respectively, then an output E of the bridge circuit 20 can be
represented by:
In the bridge circuit 20 made up in the manner described above, the
scale 12 is formed by the concave and convex grooves consisting of
the convex regions 16 and the concave regions 18. Accordingly, as
shown in FIG. 5, the magnetic field (magnetic flux .PHI.) applied
by a magnet 22 is fluctuated and deviated at the edge portions of
the convex regions 16 of the scale 12. As a result, when the output
of the bridge circuit 20 has a repetitious waveform as in the case
of a position sensor, it is possible to carry out successfully a
comparator processing for repeatedly digitizing the output of the
bridge circuit 20.
However, when the electromagnetic characteristic changing
portion(s) is/are formed singly or at spaces relative to the member
to be detected to allow generation of so-called one-pulse waveform
(1 bit) as in the case of, for example, detecting an original point
or the like of the scale, small waves are frequently generated as a
noise beside the fundamental wave due to the fluctuation of the
magnetic field caused around the electromagnetic characteristic
changing portions, which makes the comparator processing
difficult.
Now, each of the magneto-resistive elements 10a through 10d
constituting the bridge circuit 20 is passed over the
electromagnetic characteristic changing portion formed of the
convex portion 16 of the scale 12 as shown in FIGS. 6(A) through
6(H). By the way, for the electrical resistance Ra through Rd, the
resistance values thereof are not changed when the magnetic field
is applied to the element in a perpendicular direction, while the
resistance values thereof are reduced when the magnetic field is
fluctuated at the electromagnetic characteristic changing portion
of the convex region 16 to apply a transversal component to the
element. Accordingly, the output E obtained in Equation 1 varies as
follows:
For the condition shown in FIG. 6(A),
For the condition shown in FIG. 6(B),
For the condition shown in FIG. 6(C),
For the condition shown in FIG. 6(D),
For the condition shown in FIG. 6(E),
For the condition shown in FIG. 6(F),
For the condition shown in FIG. 6(G),
For the condition shown in FIG. 6(H),
As apparent from the above, a plurality of output signals are
produced on the positive side or on the negative side of the
reference voltage (zero point). Consequently, in a conventional
method for detecting the electromagnetic characteristic changing
portion, detection of the one-pulse waveform results in detection
of two output waveforms having approximately equal peaks on the
positive side or on the negative side, which can be a cause of
detection errors.
On the other hand, as disclosed in, for example, Japanese Patent
Publication No. 56-1567, there are some cases where the
electromagnetic characteristic changing portion is formed by means
of polarization and magneto-sensitive directions of two pairs of
ferromagnetic magneto-resistive elements connected in series and
orthogonally crossed each other, whereby a difference between the
outputs of the two is detected. In such a case, however, the output
waveform becomes larger in width and in area, which causes degraded
accuracy of detection.
SUMMARY OF THE INVENTION
The present invention is made to overcome the above mentioned
problems inherent to conventional arts and is directed to provide a
method and a device for detecting an electromagnetic characteristic
changing portion that are capable of detecting a single
electromagnetic characteristic changing portion with high accuracy
as well as of obtaining an output waveform having narrow peak
width.
The output E of the bridge circuit is proportional to, as apparent
from Equation (1), the difference between the two products of the
electrical resistance values of the opposing sides. Up to the
present, the conventional wisdom is that having each pair of
opposing sides of the bridge circuit formed of one element located
at a position corresponding to a convex region and one element
located at a position corresponding to a concave region would make
the first and the second terms of the right-hand side of Equation
(1) equal to each other, resulting in no output E of the bridge
circuit.
However, according to the experiments conducted by the present
inventor, concerning the distribution of the magnetic flux at the
convex region for example, the distribution on the left side of the
center of the convex region differs from, as shown in FIGS. 6(A)
through 6(H), that on the right side thereof due to a lateral bias.
In addition, the fluctuation of the magnetic flux is not
symmetrically caused at the convex region, which may be a cause of
production of the above mentioned plural output signals. Further,
the present inventor has found that an output signal can be
available even though each pair of opposing sides of the bridge
circuit is formed of one element located at a position
corresponding to a convex region and another element located at a
concave region, i.e., when they are so connected that the detected
signals are cancelled.
The present invention is made on the basis of these findings. A
method for detecting an electromagnetic characteristic changing
portion according to the present invention comprises the steps of
aligning four electromagnetic sensing elements and a member, having
the electromagnetic characteristic changing portion to be detected,
in a row in a direction of relative movement therebetween;
positioning the four sensing elements within the row in such a
manner that, when two out of the four sensing elements are
simultaneously located at a position corresponding to said
electromagnetic characteristic changing portion as a result of
relative movement, the remaining two sensing elements are located
at a position not corresponding to the electromagnetic
characteristic changing portion; and each of these four
electromagnetic sensing elements is connected in a respective one
of the four sides of a bridge circuit with each pair of opposing
sides of the bridge circuit containing one electromagnetic sensing
element located at the position corresponding to said
electromagnetic characteristic changing portion and one
electromagnetic sensing element located at the position not
corresponding to said electromagnetic characteristic changing
portion, thereby detecting the electromagnetic characteristic
changing portion.
In addition, a device for detecting an electromagnetic
characteristic changing portion according to the present invention
comprises four electromagnetic sensing elements that move
relatively to a member having the electromagnetic characteristic
changing portion to be detected and that are aligned in a row in a
direction of the relative movement; and a bridge circuit of which
each of the four sides is formed of a respective one of the four
electromagnetic sensing elements, the outer two of said four
electromagnetic sensing elements aligned in a row being in two
opposing sides, respectively, of said bridge circuit and the inner
two of the four electromagnetic sensing elements being in the
remaining two opposing sides, respectively, of the bridge
circuit.
It is preferable that, if the width of the electromagnetic
characteristic changing portion is equal to .lambda./2, each
element is formed equal to .lambda./4 or slightly smaller than
.lambda./4 while a pitch between the magneto-resistive elements is
defined as .lambda./4 or slightly larger than .lambda./4.
According to the above mentioned structure, it is possible to
remove an influence of a plurality of output waveforms due to the
fluctuation of the magnetic field generated at an edge of the
electromagnetic characteristic changing portion to obtain a single
output waveform corresponding to the electromagnetic characteristic
changing portion. In addition, it is possible to obtain an output
waveform having a narrow peak width, allowing easy and highly
accurate detection of the single electromagnetic characteristic
changing portion.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1(A) is a perspective view showing each magneto-resistive
element aligned with respect to an electromagnetic characteristic
changing portion according to an embodiment of the present
invention;
FIG. 1(B) is a view of a bridge circuit formed of these
magneto-resistive elements;
FIG. 1(C) is an elevational view of the magneto-resistive elements
and electromagnetic characteristic changing portions of FIG. 1
(A).
FIG. 2 is a typical output waveform of the bridge circuit according
to the present embodiment; and
FIG. 3 is a diagram showing exemplified output waveforms of the
bridge circuit according to the present embodiment.
FIG. 4(A) is a perspective view showing conventional
magneto-resistive elements aligned with respect to an
electromagnetic characteristic changing portion;
FIG. 4(B) is a view of a bridge circuit formed of these
magneto-resistive elements;
FIG. 5 is a perspective view showing how the magnetic field is
applied to the electromagnetic characteristic changing portion;
FIGS. 6(A) through 6(H) are views for use in describing a method
for detecting the electromagnetic characteristic changing
portion;
FIG. 7 is a diagram showing exemplified output waveforms of the
conventional bridge circuit; and
FIG. 8 is an elevational view of the magneto-resistive elements and
eletromagnetic characteristic changing portions with the magnet
being inclined at an angle to the line of relative movement.
BEST MODE FOR CARRYING OUT THE INVENTION
A preferred embodiment of a method and a device for detecting an
electromagnetic characteristic changing portion according to the
present invention is described with reference to the attached
drawing. Parts corresponding to those described in conjunction with
the background art are shown with the same reference numerals and a
detailed description thereof will be omitted.
FIGS. 1(A), 1(B), and 1(C) are views for use in describing a method
and a device for detecting the electromagnetic characteristic
changing portion according to an embodiment of the present
invention, in which FIGS. 1(A) and 1(C) show an alignment condition
of each electromagnetic sensing element while FIG. 1(B) shows a
view of a bridge circuit formed of these electromagnetic sensing
elements.
Four magneto-resistive elements 10A through 10D that serve as the
electromagnetic sensing elements are arranged in a row along the
graduation 14 of the scale 12 or a member to be detected. Each of
the magneto-resistive elements 10A through 10D is contained in a
magnetic shield case or the like (not shown), and is so held as to
be movable relative to the scale 12. In addition, if the width of
the convex region 16 or the electromagnetic characteristic changing
portion of the scale 12 is equal to .lambda./2, the width of each
of the magneto-resistive elements 10A through 10D is defined as
approximately half of that width or as equal to or slightly smaller
than .lambda./4, as illustrated in FIG. 1(C). Accordingly, when two
elements 10A and 10B out of the magneto-resistive elements 10A
through 10D are simultaneously located at a position corresponding
to the convex region 16, the other two elements 10C and 10D are
located at a position corresponding to the concave region 18.
In addition, the magneto-resistive elements 10A through 10D
constitute, as shown in FIG. I(B), a bridge circuit 30 that serves
as a detection circuit. The bridge circuit 30 differs from the
bridge circuit 20 described in conjunction with the background art
in that of the four magneto-resistive elements 10A through 10D
aligned in a row the two cross-hatched magneto-resistive elements
10A and 10D located at positions corresponding to a convex region
16 and a concave region 18, respectively, form two opposing sides,
respectively, of the bridge circuit 30. In addition, the remaining
two magneto-resistive elements 10B and 10C, located at positions
corresponding to a convex region 16 and a concave region 18,
respectively, form the other two opposing sides, respectively, of
the bridge circuit 30. Consequently, if RA through RD denote
electrical resistance of the magneto-resistive elements 10A through
10D, respectively, then an output E of the bridge circuit 30 can be
represented by:
As apparent from the above, the first term of the right-hand side
of Equation (2) is a product of the resistance value
More particularly, a typical representation of the output waveform
of the bridge circuit 30 is as shown in FIG. 2, where one large
peak is formed on each of the positive and the negative sides
relative to the zero point of the reference voltage. The reference
numerals A through H in FIG. 2 correspond to the cases of these
conditions shown in FIGS. 6(A) through 6(H), respectively.
FIG. 3 is a representation of the output waveform of the bridge
circuit 30 when each convex region 16 of the scale 12 is formed
with a width of 1 mm, each of the magneto-resistive elements 10A
through 10D is formed with a width slightly smaller than 0.5 mm,
and the pitch between the elements is 0.5 mm. As shown in FIG. 3, a
waveform having one large peak on the positive side or on the
negative side is obtained, so that it is possible to readily and
positively detect the single electromagnetic characteristic
changing portion formed for one bit such as an original point.
Besides, the narrower width of the waveform results in an improved
accuracy of detection.
In addition, the bridge circuit 30 is made up of four
magneto-resistive elements 10A through 10D, which allows
cancellation of an influence due to a change of the temperature. Of
course, the accuracy of detection is improved even when the
electromagnetic characteristic changing portion is varied
cyclically and continuously as in the case of the graduation of the
scale 12. Consequently, it becomes possible to reduce an influence
of a noise or the like to reduce detection errors. Further, the
peak can be increased by means of adjusting the magnetic field
biased laterally. In particular, a bias angle .beta., as
illustrated in FIG. 8, of 45.degree. enables an increased peak
height.
While the above mentioned embodiment has thus been described in
conjunction with the case where the RB of the magneto-resistive
element 10B located at the position corresponding to the convex
region 16 and the resistance value Rc of the magneto-resistive
element 10C located at the position corresponding to the concave
region 18, and the second term is represented as a product of the
resistance value RA of the magneto-resistive element 10A located at
the position corresponding to a convex region 16 and the resistance
value RD Of the magneto-resistive element 10D located at the
position corresponding to a concave region 18. The output E is
proportional to the difference between the first and the second
terms.
In this event, when each of the magneto-resistive elements 10A
through 10D constituting the bridge circuit 30 passes over a convex
region 16 acting as the electromagnetic characteristic changing
portion as shown in FIGS. 6 (A) through 6(H), the output E varies
as follows:
For the condition shown in FIG. 6(A),
For the condition shown in FIG. 6(B),
For the condition shown in FIG. 6(C),
For the condition shown in FIG. 6(D),
For the condition shown in FIG. 6(E),
For the condition shown in FIG. 6(F),
For the condition shown in FIG. 6(G),
For the condition shown in FIG. 6(H),
electromagnetic sensing elements are ferromagnetic
magneto-resistive elements 10A through 10D, the electromagnetic
sensing elements are not limited to the ferromagnetic
magneto-resistive elements and can be semiconductor
magneto-resistive elements, Hall elements, coils, or the like. In
addition, while the above mentioned embodiment has thus been
described in conjunction with the case where the electromagnetic
characteristic changing portion is formed of the convex regions 16,
the electromagnetic characteristic changing portion may be formed
by means of polarization or the like. Furthermore, while the above
mentioned embodiment has thus been described in conjunction with
the case where the scale 12 is formed in straight line, it can be
applicable to a rotary encoder or the like.
As described above with the four electromagnetic sensing elements
aligned in a row, according to the present invention, each pair of
two opposing sides of the bridge circuit is formed of one
electromagnetic sensing element located at a position corresponding
to the electromagnetic characteristic changing portion and one
electromagnetic sensing element located at a position not
corresponding to the electromagnetic characteristic changing
portion, respectively. As a result, it is provided a 1-force
waveform having one peak that is narrow in width on one side
relative to the reference voltage and it is possible to detect a
single electromagnetic characteristic changing portion such as an
original point with high accuracy.
INDUSTRIAL APPLICABILITY
The present invention is useful as a method and a device for
detecting, with high accuracy, an electromagnetic characteristic
changing portion formed on a member to be detected, such as a
position detecting device of a hydraulic cylinder, a linear scale,
or a rotary encoder.
* * * * *